Canine disseminated peritoneal angiomatosis with arterial differentiation in a 10‐month‐old Rhodesian Ridgeback

A 10‐month‐old, male entire Rhodesian Ridgeback was presented with a 1‐week history of vomiting, small and large intestinal diarrhoea, hyporexia and weight loss. Physical examination revealed a palpable abdominal mass. Abdominal ultrasonography and contrast computed tomography demonstrated multiple cystic masses of varied size and wall thickness with no appreciable origin. An exploratory laparotomy revealed multiple mass lesions throughout the mesentery, located adjacent to blood vessels and varying in size from approximately 2 mm up to 13 cm in diameter. In histologic sections, the nodular structures resembled thick‐walled arteries. Immunohistochemistry confirmed positive cytoplasmic immunoreactivity for von Willebrand factor, CD31 and smooth muscle actin. This is, to the authors’ knowledge, the first case of disseminated peritoneal angiomatosis with arterial differentiation in the dog. The dog was euthanased due to the progressive nature of the mass lesions.